1. Field of Invention
This invention relates to a method of assay of water to determine an aspect of its biological and chemical quality, using a luminescent reaction.
2. Description of Prior Art
Pollution is an endemic problem In water throughout the world. Many tests exist to detect pollutants in water. Generally pollutants have the effect of decreasing the oxygen availability within the water. Such oxygen deprivation may be detrimental to the extent of disrupting the delicate ecosystem within the source of water. In rivers, ponds, lakes and the like this can result in the death of both plantlife and wildlife as the levels of pollutants increase and correspondingly the amount of oxygen in the water decreases.
The oxygen levels in a sample of water indicates the amounts or presence of pollutants. Several methods exist for measuring oxygen in water. The Winkler titration is a preferred method for measuring dissolved oxygen. More sophisticated methods involve the use of oxygen electrodes. Of wider use in the monitoring of pollution has been the biochemical oxygen demand (BOD) test. In it the decrease In dissolved oxygen concentration resulting primarily from biological action (bacterial oxidation) is measured over a period of 5 days at 20.degree. C. The BOD test suffers from several drawbacks. It fails to mimic the natural processes occurring in the water--this is primarily due to the test being carried out in the dark. It can also be complicated by lack of suitable bacteria in the sample, or the presence of toxic compounds that prevent the breakdown of pollutants. Additionally, the oxygen content of the sample may change during storage. Generally, many considerations have to be taken into account to obtain a true value. Results have a high degree of variability. These and other related methods are discussed in Standard Methods for the Measurement of Water and Waste Water, 15th edition, Amer. Pub. Health Assoc. 1979.
Recently, the National Rivers Authority have recommended that the current 5 day BOD test be replaced by measuring Total Organic Carbon (TOC) (Laboratory Equipment Digest, August 1991, 41-42). This method also has several drawbacks. It involves UV radiation and the use of concentrated nitric acid, requiring special laboratory conditions. Inorganic carbonates, bicarbonates and carbon dioxide present in the water interfere with the reaction and must first be removed--hence the end result is often inaccurate.
These methods supply only limited information, are lengthy and require specialised laboratory apparatus and technicians.
There is therefore a need for a rapidly functioning method of assessing the biological and chemical quality of a water sample, which can be carried out simply and on site.
Further prior art is mentioned after the "Summary of the Invention", without which its context would not be clear.